The invention concerns a plastic body in the form of a film, for example a transfer film, in particular a hot stamping film, or a laminating film or provided with such a film, as set forth in the classifying portion of claim 1, and a process for the production of a multi-color image on or in such a plastic body.
WO 96/35585 discloses various configurations of plastic bodies and more specifically solid bodies or coatings which respectively contain a mixture of various pigments. In the embodiments described therein the pigment mixture is composed of three pigment components, more specifically a yellow pigment, a magenta pigment and a cyan pigment. Color marking is effected on the plastic body by laser treatment. The color marking is produced by bleaching of the pigments with the laser treatment. The laser conditions are respectively set specifically with variations in the wavelength to obtain given colors. The respective specific wavelength used is previously ascertained by light absorption measurements on the pigments, and more specifically the absorption wavelength at the absorption maximum of the pigment is ascertained in each case. Pigments are used which have only a single absorption maximum. That is intended to ensure that the laser treatment produces a color which corresponds to the laser light and the duration of the laser treatment and the intensity of the laser light can be of the same value for each color. In the described embodiments with the pigment mixture consisting of yellow pigment, magenta pigment and cyan pigment, the laser treatment involves using violet laser light at a wavelength of 430 nm, blue laser light at a wavelength of 470 nm, yellow laser light at a wavelength of 575 nm and laser light which is referred to as orange at a wavelength of 650 nm. In that way the aim is to produce various color markings on the plastic body by means of the laser treatment by suitable adjustment of the laser wavelength with the laser conditions being otherwise the same. The colors are produced by complex mixing of the pigments which are bleached at the same time at the respective laser wavelength. A disadvantage is that no method is specified, with which all colors could be produced.
WO 98/19868 describes a correspondingly operational process for producing color markings, which however involves using special yellow, magenta and cyan pigments, which more specifically can be activated by way of UV light in a first step and are bleached only in a subsequent second step.
DE 199 55 383 A2 which is not a prior publication describes a process for producing color markings by laser treatment, which operates using a two-coordinate beam deflection device with a focusing device, employing a special mirror device. The body to be marked has a mixture of cyan pigment, magenta pigment and yellow pigment, those pigments being selectively bleached by red laser light, green laser light or blue laser light. An essential point is that this process does not provide for using a film, preferably a multi-layer film, in the form of a transfer film or in the form of a laminating film or such a film applied to a substrate.
It is also known from WO 94/12352 to produce bright color markings on a plastic body which includes a pigment mixture and which can be in the form of a solid body or a coating, by laser treatment using different wavelengths. The coloring effect is implemented by virtue of the pigments altering their color by color change when the laser treatment is carried out. The laser conditions are randomly selected in each case. A process for specifically producing any colors is also not specified here. The number of colors produced in this way is greatly limited.
EP 0 327 508 discloses a process in which a laser-sensitive dyestuff A and a laser-insensitive dyestuff B are contained in two separate mutually superposed layers or alternatively in a common layer and the dyestuff A is bleached by laser treatment while the dyestuff B is not bleached or is bleached only slightly. A color marking is obtained with the laser treatment. The process does not provide for any variation in the laser conditions in respect of wavelength and only a single-color marking, that is to say at a maximum a two-color image, is to be produced in this fashion.
EP 0 190 997 B1 discloses a process in which a plastic plate or a plastic layer in the form of a coating on a metal flake contains an additive which is intended to discolor upon laser treatment, more specifically either by color change from one color to another or by transformation to black. It is not possible with that process to produce color markings involving different colors.
DE 37 38 330 A1 discloses a laser inscription process for use in relation to surfaces with a pigment coating, wherein pigments of the pigment coating change their internal molecular structure at different temperatures, and produce different colors. The specific surface temperatures are locally achieved with the laser irradiation effect, thereby producing colored laser markings.
GB 2 240 948 A also describes laser inscription of identity cards. Here laser inscription is effected by the removal of different color layers. The laser marking produced in that case appears as a colored marking.
DE 41 31 964 A1 describes laser inscription of a multi-layer film with a metal layer and a hologram structure. The inscription operation is effected by region-wise destruction of the metal layer bearing the hologram.
EP 0 420 261 discloses a hot stamping film with a hologram structure, which is individualised by way of laser treatment for the purposes of safeguarding it against forgery. A change in material or color or removal of portions in the layer structure of the film is effected by means of the laser beam. This procedure does not involve multi-color marking.
EP 0 416 664 B1 discloses producing black markings by a laser marking operation in plastic bodies or film layers. The marking is produced by laser-induced blackening of the laser-sensitive component molybdenum sulfide contained in the plastic material.
DE 44 10 431 describes a process with which person-related data are applied to an identity card by laser inscription, the identity card having an anti-copying element applied by a transfer process. In the laser inscription procedure, an identification in the form of a row of digits is applied by a portion of the row of digits being produced in the anti-copying element and a further portion of the row of digits being applied in an adjoining region of the identity card. Laser inscription is effected by way of local demetallisation in the metal layer of the anti-copying element or by blackening of the treated region of the identity card respectively.
EP 0 219 011 B1 describes a special process for laser inscription on identity cards. In this process, black markings are produced in different transparent layers of the card by means of a laser. Parallactic images are produced in that way in the mutually co-operating transparent layers.
It is known from DE 195 22 397 A1 to produce bright inscription by laser treatment of plastic layers containing pigments. That is effected by laser bleaching of the pigments contained therein.
It is further known for example from EP 0 537 668 and DE 813 08 61 U1 for layers in the layer structure of transfer films to be removed in a region-wise manner by laser treatment in order in that way to produce inscriptions therein.
It is also known for example from EP 0 741 370 B1, DE 43 33 546 A1 or U.S. Pat. No. 4,911,302 to produce markings by laser treatment of laminate bodies, by laser-induced melting of the material, in order then to transfer those inscriptions while still in the molten state on to another body.